Relationship between primary percutaneous coronary intervention time of day, infarct size, microvascular obstruction and prognosis in ST-segment elevation myocardial infarction

Whether the time of day of primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with infarct size, microvascular obstruction (MVO), and prognosis is uncertain. We compared infarct size assessed by cardiac MRI (CMR) and clinical outcomes in STEMI patients according to the pPCI time of day from a large, individual patient-data pooled database.We pooled patient-level data from five randomized pPCI trials in which infarct size was measured within 1 month by CMR. Patients were categorized according to the pPCI time of day.Among 1519 patients with STEMI, 794 (52.2%) underwent pPCI between 8:00 h and 15:59 h, 431 (28.4%) between 16:00 h and 23:59 h, and 294 (19.4%) between 24:00 h and 7:59 h. Infarct size was assessed in 1331 patients at a median of 3.0 days (interquartile range 2.0-5.0) after pPCI. Compared with patients who underwent PCI between 8:00 h and 15:59 h, infarct size was not significantly different for patients undergoing PCI from 16:00 h to 23:59 h [adjusted difference -0.7%, 95% confidence interval (CI) -3.1 to 1.7%, P = 0.46] or 24:00 h to 7:59 h (adjusted difference 0.9%, 95% CI -1.2 to 3.1%, P = 0.29). The time of day of pPCI was also unrelated to MVO and the 1-year risks of death or heart failure hospitalization.In this large-scale, individual patient data pooled analysis, no association was found between the time of day of pPCI and infarct size, MVO, or prognosis after STEMI.